If the default browser is not playing videos, download an alternate mobile browser such as Google Chrome.

Use a different network

If you are unable to play videos on your 3G/4G network, try connecting to a wifi network to see if you can watch videos.

Check for the latest system updates

For optimal performance keep your device updated with the latest system updates. On Android, navigate to Settings > About Phone > System updates and touch Check now. On iOS, navigate to Settings > General > Software Update.